10 MORE Oldest Characters In The Star Trek Universe
4. Nagilum
Nagilum is a creature that exists outside of the known boundaries of reality. The trials that it put the crew of the Enterprise-D through were those of a scientist toying with lab rats, but there is something deeper in its fascination with corporeal life. The will to use pain simply to see the reaction is, sadly, a very human trait.
As normal physics don't seem to affect Nagilum, guessing the creature's age is hard. It seemed as though Where Silence Has Lease saw the first encounter between humanity and the face in the clouds, but that is an awfully long time for Nagilum to sit there in space, alone.
It may exist on a plain similar to the Prophets of the Bajoran Wormhole, which would make it both ageless and out of sync with what humans understand as time. It may well be that it's as much an infant as anything else, which could only add to its danger. It simply may not know any better than to kill so that it can see the effects of death.
Nagilum is one of the more frightening prospects of the Milky Way galaxy. Perhaps some things that are best left alone.